Space

Hubble reveals first pictures of Milky Way’s formative years

NASA’s Hubble Space Telescope has revealed the first visual evidence of how our home galaxy, the Milky Way, assembled itself into the majestic pinwheel of stars we see today.

Astronomers used Hubble’s deep-sky surveys to study the evolution of 400 galaxies similar to the Milky Way and noted their appearance at various stages of development over a time span of 11 billion years. Judging from images of these far-flung galaxies, they found the Milky Way likely began as faint, blue, low-mass object containing lots of gas. Gas is the fuel for star birth and the blue color is an indicator of rapid star formation.

They also found the Milky Way probably was a flat disk with a bulge in the middle, both of which grew simultaneously into the majestic spiral seen today. The sun and Earth reside in the disk and the bulge is both full of older stars and home to a supermassive black hole that probably grew along with the galaxy.

“For the first time, we have direct images of what the Milky Way looked like in the past,” said study co-leader Pieter G. van Dokkum of Yale University in New Haven, Conn. “Of course, we can’t see the Milky Way itself in the past. We selected galaxies billions of light-years away that will evolve into galaxies like the Milky Way. By tracing the Milky Way’s siblings, we find that our galaxy built up 90 percent of its stars between 11 billion and 7 billion years ago, which is something that has not been measured directly before.”

The Hubble telescope’s superior resolving power, with which it can see extremely fine details, allowed the researchers to study how the structure of the Milky Way changed over time. At the peak of star formation, when the universe was about 4 billion years old, the Milky Way-like galaxies were pumping out about 15 stars a year. By comparison, the Milky Way today is creating only one star a year.

“You can see that these galaxies are fluffy and spread out,” said study co-leader Shannon Patel of Leiden University in The Netherlands. “There is no evidence of a bulge without a disk, around which the disk formed later.” Team member Erica Nelson, of Yale University, added: “These galaxies show us the whole Milky Way grew at the same time, unlike more massive elliptical galaxies, in which the central bulge forms first.”

To identify the far-flung galaxies and study them in detail, the research team used three of the largest Hubble programs, the 3D-HST survey, the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey and the Great Observatories Origins Deep Survey. These surveys combined spectroscopy with visible and near-infrared imaging by Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys.

The research team’s analysis involved measuring the distances and sizes of the galaxies. The astronomers calculated the mass of each galaxy from its brightness and colors. They selected the galaxies in their census from a catalog they compiled of more than 100,000 galaxies. The survey galaxies are consistent with computer models, which show at early stages, a majority of the bulges of spiral galaxies were built up at the same time as their corresponding disks.

“In these observations, we’re capturing most of the evolution of the Milky Way,” explained team member Joel Leja of Yale University. “These deep surveys allow us to see the smaller galaxies. In previous observations we could only see the most luminous galaxies in the distant past, and now we can look at more normal galaxies. Hubble gives us the shapes and colors of these spirals as well as their distances from Earth. We also can measure the rates at which each part of the galaxies grew. All of this is difficult to do from the ground.”

The team’s results were published July 10 in The Astrophysical Journal Letters. A second paper appears in the Nov. 11 online edition of The Astrophysical Journal.

Local military discounts

News: Israel lobbies for more missile defense funds than Obama sought - For the second consecutive year, Israeli officials have asked the U.S. Congress to add more than $300 million to President Barack Obama’s budget request for their nation’s missile-defense programs. Business: Inside one of the most intense, and unusual, Pentagon contracting wars - The much-anticipated...

Italy resumes Navy exercise amid new tensions over Libya The Italian Navy is resuming exercises in the Mediterranean Sea, including near the coast of Libya, amid concerns about rapidly deteriorating security in the North African nation. The exercise began March 2 and includes anti-submarine, anti-aircraft and anti-ship training operations. The exercise was suspended for a...

Two Boeing 702SP (small platform) satellites, the first all-electric propulsion satellites to launch, have sent initial signals from space, marking the first step toward ABS, based in Bermuda, and Eutelsat, based in Paris, being able to provide enhanced communication services to their customers. Whatís more, the satellites were launched as a conjoined stack on a...

General Atomics Aeronautical Systems, Inc. and SENER, a leading Spanish engineering company, announced March 2 that they have signed a teaming agreement that promotes the use of the multi-mission Predator B® RPA to support Spain’s airborne surveillance and reconnaissance requirements. GAASI is a leading manufacturer of Remotely Piloted Aircraft systems, radars, and electro-optic and relate...

Raytheon has delivered a second Visible Infrared Imaging Radiometer Suite instrument to support the National Oceanic and Atmospheric Administration’s Joint Polar Satellite System mission. The second VIIRS unit will fly ab...

Information

Publisher

Aerotech News and Review is published every Friday serving the aerospace and defense industry of Southern California, Nevada and Arizona. News and ad copy deadline is noon on the Tuesday prior to publication. The publisher assumes no responsibility for error in ads other than space used.

Disclaimer

The appearance of advertising in this publication, including inserts or supplements, does not constitute endorsement by the Department of Defense, U.S. Air Force, U.S. Army, U.S. Navy, U.S. Marine Corps, or Aerotech News and Review, Inc., of the products or services advertised.